Methods and apparatus for automatical-
ly threading strip rolling mills



May 25, 1965 G. E. TERWILLIGER METHODS AND APPARATUS FOR AUTOMATICALLYTHREADING STRIP ROLLING MILLS 3 Sheets-Sheet 1 Filed NOV. 28, 1961George A: Emu/Wager fi/ls Attorney fr? ven or May 25, 1965 5. E.TERWILLlGER METHODS AND APPARATUS FOR AUTOMATICALLY THREADING STRIPROLLING MILLS Sheets-Sheet 2 Filed Nov. 28, 1961 fr) vent'or' Gear M y1965 s. E. TERWILLIGER 3,134,933

METHODS AND APPARATUS FOR AUTUMATICALLY THREADING STRIP ROLLING MILLSFiled Nov. 28, 1961 3 Sheets-Sheet 3 In en 60/" 6e or gfe ETrW/VQ'gJePby 1 AM 4 M /7/.'s Attorney United States Patent Ofi Fice 3,184,938Patented May 25, 1965 3,184,938 METHGDS AND APPARATUS FOR AUTOMATICAL-LY THREADING STRIP ROLLING MILLS George E. Terwiiiiger, Schenectady,N.Y., assignor to General Electric Company, a corporation of New YorkFiled Nov. 28, 1961, Ser. No. 155,408 18 Claims. (CI. 72-11) Myinvention relates to rolling mills of the type in which a strip ofmaterial is reduced in thickness by subjecting it to pressure atdisplaced points as the strip passes through the mill and, inparticular, to methods and apparatus for rapidly and automaticallythreading material through such a mill.

It is customary in reducing the size of material such as strip steel,for example, to pass it through a cold rolling mill which comprises aseries of rolls or pressure points arranged in tandem. At the presenttime it is customary to manually insert the front end of the strip intothe first roll and guide it as it proceeds through the successive rollsuntil it reaches the final toll. Thereafter, the speed of rolling may beincreased. Such a procedure is both time consuming and also requiresunwanted handling of the material. It would be extremely desirableinstead to have a system in which the strip can be physical transportedbetween adjacent stands or rolls by means of tables or guides and forautomatically steering the head end of the strip so that it enters eachsuccessive stand or roll on the center line thereof. One of the problemsencountered in such a tandem rolling mill is the production ofhorizontal curvature in the strip caused by unequal percent reductionacross the width of the strip which, in turn, may be caused by, forexample, improper leveling of the mill, unequal pressures across thewidth of the rolls, improper lubrication, or unequal thickness of thestrip material itself. Also, difiiculty is encountered during the finalportion of the rolling operation when the strip becomes thin andflexible to provide vertical support for the strip and still preventbuckling of the strip as it is pushed along such support.

It is a prinpieal object of my invention to provide new and improvedmethods and apparatus for automatically threading a strip of materialinto a tandem cold mill.

it is still another object of my invention to provide new and improvedmethods and apparatus which permit rapid and automatic threading ofstrip material through a rolling mill while still preventing buckling ofthe material.

It is still another object of my invention to provide new and improvedapparatus for automatically threading strip material through a tandemrolling mill in which the naterial is automatically centered betweensuccessive pressure points so that it advances substantially along thecenter line of the mill.

One of the features of my invention consists in sensing the position ofthe edge of a strip of material relative to the center line of the rollsof a tandem mill after it passes through a stand or pressure point andcontrolling the pressure on the edge of the strip at such a pressurepoint to produce centering of the strip so that it advances along thecenter line of the mill. In one embodiment, a plurality of sensorsengage the edges of such a strip of material to produce voltages orsignals which are added algebraically to provide means for controllingthe pressure applied to the strip at a previous point in travel. Inaccordance with another feature of the invention, increased stiffness tothe materialbeing reduced in thickness to inhibit its dropping below adesired horizontal plane is pro vided by exerting vertical forces on thestrip material to produce a curvature of the material in a verticalplane through the material. As used herein, the term threading" means topass the initial portion of strip material being reduced in thicknessthrough or past the successive pressure points of a rolling mill fromits entry end to its exit.

The invention, both as to its organization and operation, together withfurther objects and advantages thereof, may best be understood byreference to the following description taken in connection with theaccompanying drawings, in which FIGURE 1 is a schematic vertical view ofa tandem rolling mill embodying my invention;

FiGURE 2 is a plan view of the mill of FIGURE 1 taken along the lines2-2;

FIGURE 3 is a circuit diagram illustrating certain features of theinvention;

FIGURE 4 illustrates one of the sensors used in the mill of FIGURE 1;

FIGURE 5 is a cross-section view of the material stiffening deviceemployed in apparatus embodying my invention;

FIGURE 6 is a perspective view of an alternative material stiffeningdevice;

FIGURES 7-9 are schematic drawings illustrating certain features of myinvention; and

FIGURE 10 is a schematic drawing of a modification of the mill of FIGURE1.

In FIGURE 1 there is shown a typical tandem rolling mill illustrated inthis instance as comprising six stands, l d. Each stand conventionallycomprises a frame 7 in which is supported a pair of working rolls 8 and9 which exert pressure on a strip of material 10 whose thickness is tobe reduced. The pressure upon the strip 10 is exerted by rolls 8 and 9through backup rolls 11, 12 and a pressure exerting device, such as thescrew 13, whose position is controlled by means of a motor 14.

In a typical mill of the type illustrated in FIGURES l and 2, thethickness of a strip of material 10 as it passes through the stands 1-6is reduced each time it passes through a pressure point created by theopposed rolls 8, 9 of each stand. The amount of reduction in each standis determined by the spacing between each pair of rolls 8, 9, thesespacings being preset so that the strip of material 10 as it emergesfrom the mill after passing through the rolls of stand 6 is of a desiredfinal thickness. In a mill of this type, it has been customaryheretofore to initiate operation of the mill by manually threading orguiding the strip of material 10 through each of the successive stands.Such an operation is limited to relatively low threading speeds and istime consuming. In accordance with my invention, I provide means forperforming this function automatically, allowing higher threading speedsand increased production.

In order to automatically guide a strip of material through the millillustrated, I provide means for sensing the position of the edge of astrip relative to the center line of the mill after it has passedthrough a pressure point. Such a means is illustrated in FIGURES 1 and 2as including three sets of two closely spaced pairs of rollers andcarrying arms 15, 16 and 17, 18 positioned at points spaced along thepath of travel of the strip 10 and arranged to engage and be rotated bythe opposite sides of the strip after it emerges from the engagementwith the work rolls 8, 9 of each of the stands 1, 2 and 3. As will beexplained later in connection with the diagram shown in FIGURE 3,rotation of arms 15-18 is operative to sense the position of the edge ofthe strip relative to the center line of the mill and control subsequentlateral movement of the strip by controlling the pressure exerted by thework rolls 8, 9 of the preceding stand to produce a horizontal bendingof the strip in a direction to guide it along the center line of themill. Such bending is in a .1 direction to correct any horizontalcurvature of the strip which may e caused, as it passes through thefirst several rolls of the mill, by either improper leveling of themill, unequal pressures across the width of the rolls, or unequalthickness in the cross section of the entering strip material itself.

After the sensing means -18 have produced a corrective curvature in thehorizontal position of the strip of material 10, the need for anyadditional corrective bend ing is determined by an additional pair ofsensing means comprising rotatable arms 19, displaced from arms 15-18along the path of travel of the strip 10. Through circuit arrangementsto be described later, sensing means 19, 20 provide an additionalcorrective adjustment of the pressure across the width of the stripexerted by rolls 8, 9 of the preceding stand.

After a strip of material has been reduced in thickness by passingthrough several of the stands, it may become sutficiently thin that itexhibits a tendency to either droop below a desired horizontal positionor buckle as it passes across supporting tables, not illustrated,conventionally employed to support the strip of material betweensuccessive later stands in the mill, such as, for example, stands 4, 5and 5, 6. In order to PTcVCIli such undesired buckling of the strip, Iprovide means for exerting a vertical force on the strip to produce acurvature of the strip in a vertical plane and increase its stiffness inits direction of travel. The strip stiifening means in the case of themill illustrated in FIGURES 1 and 2 comprises two sets of retractablerollers 21, 22, 23. Rollers 21, 22 positioned below the strip alongopposite edges thereof and roller 23 positioned above the center of thestrip, are movable in converging directions to engage the moving stripof material and cause it to bend to an arcuate shape in a verticalplane.

The schematic drawing of FIGURE 3 illustrates the operative connectionsbetween the sensing means 15-20 and the electrical circuits throughwhich pressure is exerted on the moving strip. Each of the sensing meansmay comprise a pivoted arm which is connected through a pair of gears24, 25 to a variable rheostat. Rheostats 26. 27 associated with arms 15,16, respectively, are connected to a first amplifier 28. Rheostats 26,27 are connected across a source of unidirectional voltage illustratedby conductors 29, 3t) and a grounded conductor 31. Thus, rheostat 26 isconnected between conductors 30, 31 to supply to amplifier 28 a voltagewhose magnitude varies with the position of the left hand edge of strip10 from the center line of the mill. Similarly, rheostat 27 supplies tothe amplifier a voltage whose magnitude varies with variation of theright hand edge of strip 10 from the center line of the mill. A typicalform of rheostat 26 is shown in FIGURE 4 in which one end of therheostat is connected to ground and the other end connected to a pointof supply voltage while the variable arm thereof provides anintermediate value of voltage which is supplied to amplifier 28.

With reference again to FIGURE 3, the rotatable arms 17, 18 associatedwith the second set of sensors are connected through similar gears 24,25 to variable rheostats 32, 33. Rheostats 32, 33, in a manner similarto rheostats 26, 27, likewise supply to amplifier 28 a pair of voltageswhose magnitudes vary respectively with the position of the left andright hand edges of strip 10 from the center line of the mill. Movementof arm 18 and, likewise, of arm 17 if desired, is etlective to close apair of contacts 34, connected in the energizing circuit of relay 36whose operation effects closure of contacts 37, 38 connccted in circuitbetween the output of amplifier 28 and an amplifier 39. Energization ofrelay 36, likewise, closes contacts 40, 41 connected between amplifier39 and a control device 42. Device 42 may be, for example, a siliconcontrolled rectifier circuit or an amplidyne circuit which suppliesexcitation voltage to the field windings 43, 44 ot a pair of directcurrent generators 45, 46. Generators 45,

46, in turn, supply operating potential to motors 14, 14' which controlthe rotation of screws 13, 13' and the pressure exerted through rolls 8and 9 on strip material 10. As illustrated, motors 14, 14' effectrotation of worm drives 47, 47 which engage cooperating gears attachedto the upper ends of screws 13, 13.

Energization of relay 36 is effective also to open normally closedcontacts 43, 49 connected in the circuit of a screw down control 50 incircuit between conductors 29, 30, 31 and amplidyne control 42. Control50 is adjusted at the beginning of each run of strip material to supplypredetermined voltages to control 42 to obtain a desired pressure onstrip 10 between rolls 8 and 9.

Associated with arms 19 and 20 are a pair of variable rheostats 51, 52which supply, respectively, to an amplifier 53 voltages varying with thepositions of the left hand and right hand edges of strip 10 from thecenter line of the mill at this point of its travel. The output ofamplifier 53 is supplied through a peak holding circuit 54 to amplifier39 to provide a voltage which is combined with the voltage suppliedthereto from amplifier 28.

The operation of my apparatus for automatically threading a striprolling mill may best be explained by reference to FIGURE 3 and FIGURES79. As the strip material 10 emerges from one of the stands 1- 3, itfirst encounters the rotatable arms 15, 16 which supply to amplifier 28two voltages whose algebraic sum is indicative of the variation of thecenter line of the strip front the center line of the mill. The edges ofthe strip 19 next engage arms 17, 18 whose rotation, likewise, suppliesto amplifier 28 a second set of voltages whose algerbraic sum isindicative of the variation of the center line of the strip from thecenter line of the mill. Amplifier 28 is eflective to resolve the fourvoltages supplied thereto and provide through amplifier 39 to amplidyne42 a control voltage varying with the distance between the center lineof the strip and the center line of the mill. If the sum of the voltagesupplied by rheostats 26, 27 is exactly equal in magnitude but ofopposite polarity to the sum of the voltages supplied by rheostats 32,33, this condition indicates that while the center line of the strip isnot exactly along the center line of the mill, nonetheless, there is nocurvature in the horizontal direction of the head end of the strip. Onthe other hand, if these two voltages are not exactly equal, theiralgebraic sum varies in magnitude with the curvature of the front end ofthe strip. Accordingly, such a voltage is supplied to control device 42to vary the excitation of the fields 43, 44 of generators 45, 46.Preferably, these fields are poled in opposite directions so that theeffect is to produce opposing changes in the output voltages ofgenerators 45, 46. Supplying such opposite voltages to motors 14, 14 iseffective to increase the pressure on one side of strip 10 and,simultaneously, decrease the pressure on the opposite side. The over-alleffect is to produce a rapid variation in the pressure applied acrossthe width of the pressure point defined by rolls 8, 9 and produce adecrease in thickness of one side of strip 10 and an increase in theopposite side so that the strip is elongated on one side to produce astrip that has no horizontal curvature and is travelling parallel to themill center line.

The foregoing result is illustrated in FIGURES 7 and S in which strip10, in emerging from the stand, has a horizontal curvature which directsit toward the bottom of the drawing as illustrated; i.e., toward theright of the center line of the mill. Contacting rolls 1548 produces achange in the pressure between the rolls 8, 9 of the preceding standsuch that the strip cmerging from the rolls travels parallel to the millcenter line. The strip emerging from the stand will continue to have nohorizontal curvature until the head end of the strip engages rolls 19,20 as illustrated in FIGURE 8. Since the strip at this point has aninitial section having horizontal curvature which is now directed to theright hand side of the center line of the mill, rotation of arms 19, bystrip 10 is effective to operate rheostats 51, 52 and amplifier 53 toprovide to amplifier 39 a voltage which, when algebraically added to thevoltage supplied from amplifier 28, provides a corrective voltage tocontrol device 42 to again adjust the voltages across motors 14, 14'.The pressure across the rolls 8, 9 of the preceding stand is nowreadjusted to produce a horizontal curvature of the strip in a directionto direct the head end of the strip toward the center line of the millso that by the time the head end of the strip reaches rolls 8, 9 of thenext succeeding stand, its center line is substantially along the centerline of the mill.

After the head end of the strip has entered the gap between the rolls 8,9 of the next succeeding stand, I provide means for disabling thecontrol circuits operating to vary the pressure on the strip at thepreceding stand and to return that pressure to a desired preset value.This means comprises a pair of contacts 55, 56 operating from a pressureresponsive device 57 positioned below the bearing block 58 of the stand(not shown in FIG- URE 3) which the strip is now entering. Contacts 55,56 are connected in the circuit of relay 36 and when opened by entry ofthe strip into the gap between rolls 8, 9 of the next succeeding standare effective to deenergize relay 36, thus opening contacts 40, 41 andclosing contacts 48, 49 and connecting the predetermined screw downcontrol voltage supplied by control to control device 42 and reset thepressure on strip 10 to a desired value.

As explained previously, the circuits and controls described areduplicated between each set of stands 1, 2, 2, 3, and 3, 4. Throughoperation of these circuits and controls, the strip 10 is automaticallythreaded through the first four stands of the mill. By the time itadvances to this position in its travel through the mill, the strip issubstantially aligned along the center line of the mill, and thepressures exerted on the strip through the first three stands are of apredetermined value established to provide uniform reduction of thethickness of the strip so that the strip is of a desired uniformthickness by the time it enters stand 4. At this point, however, thestrip usually is sutficiently thin that it shows a tendency to droop ifunsupported or buckle if it is slid along the supporting tablesconventionally used between stands 4, 5 and 5, 6. In order to preventsuch buckling, the strip is curved in a vertical plane to increase itsstillness in its direction of travel, Such stiffness in the case of themill shown in FIGURES l and 2 is provided through operation of rollers21-23 illustrated in FIGURE 5. Each of the rollers 2123 is carried on arod 59 movable by means of a control 60. Preferably, the rods 59 of therespective rollers 21-23 move in converging direc tions so that roller23 exerts a force vertically downward at the center of the strip 10while rollers 21, 22 engage the outer portions of the strip to bendthese outer portions in an upward direction. Controls 60 may compriseeither conventional hydraulic controls or may comprise solenoidsoperating through a contact arm 61 engaged by the strip 1i]. After thestrip has advanced, for example, through the distance between stands 4,5 and enters stand 6, pressure switch 58 on stand 6 is operative todisable the stillness increasing apparatus between stands 4 and 5.Similarly, operation of the strip stiffening means between rolls 5 and 6is effected when the strip engages contact 61 between stands 5 and 6 andis discontinued when the strip enters stand 6.

Many well known alternative arrangements. for bending or bowing strip 10to increase its stifiness are apparent. One such alternative form ofstrip stiffening means is illustrated in FIGURE 6 and comprises asupporting table 62 formed of a suitable material which will not scratchthe strip, such, as, for example, a pair of separable maple blocks, andhaving an entry 63 therein which is adapted to receive the strip 1t]upon its emergence from the pressure point of the preceding stand andbend the strip slightly so that its stiffness is increased until itenters the gap of the rolls 8, 9 of the next succeeding stand. Asillustrated in FIGURE 6, the entry point of slot 63 has sufiicientheight to it to facilitiate receiving the head end of the strip. Theslot 63, however, narrows slightly laterally and deepens verticallytoward the right hand or exit end of the slot and also is arcuate shapedso that the strip has an arcuate shape when it emerges from slot 63,which shape it retain until it enters the gap between the rolls of thenext succeeding stand.

In FIGURE 10, I have shown an alternative arrangement for controllingthe horizontal curvature of a strip of material being reduced inthickness to facilitate threading of a rolling mill. In thisarrangement, the contact arms 17', 13 are eliminated and the voltageproduced by adding algebraically the voltages supplied by movement ofarms 15, 16 is used to control the pressure across the width of thestrip in the preceding stand. A second pair of arms 64, 65 is positionedfurther along the travel of the strip than the arms 17, 18 of the millof FIGURES 1 and 2 and in a position which is intermediate the positionof the arms 17, 18 and 19, 20. Arm 64, 65 are operative through variablerheostats of the type shown in FIGURE 3 to produce a control voltagewhich is algebraically added to the control voltage supplied by arms 15,16 to alter any adjustment of the pressure across the rolls of thepreceding stand produced through operation of arms 15, 16. The combinedvoltages produced by the two sets of arms l5, l6 and 64, 65 are thuseffective to provide corrective bending of the head end of the stripsufficient to cause its entry into the next stand along the center lineof the mill. In many instances, contacting the edges of the advancingstrip at only two points and in some cases at only one point in its pathof travel will suihce to control threading of the mill. In either case,whether the arrangement of FIGURES l and 2 or of FIGURE 10 is employed,by my invention a tandem rolling mill can be successfully automaticallythreaded to facilitate operation of the mill. By combining the featureof directing the path of the head end of the advancing strip utilizingthe arrangements shown in FIGURES 79 or in FIGURE 10 and the arrangementfor producing stiffness in the strip during the later of its travelthrough the mill using the arrangements of either FIGURE 5 or FIGURE 6,I am able to provide a tandem mill which can be automatically threadedrapidly and safely.

In many instances it is desirable to control the rate of adjustment ofpressure and in some instances to vary that rate with the speed of thestrip moving through the mill. To effect such control, I have providedin the apparatus illustrated in FIGURE 3 means responsive to the rate ofchange of position of adjusting screw 13 which may comprise, forexample, a tachometer or alternative speed responsive device 66 arrangedto provide a signal varying in polarity and magnitude with direction andspeed of rotation of screw 47. The output signal of device 66 issupplied through a time constant circuit comprising resistance 67 andcapacitance 68 and contacts 69. 70 to amplifier 3?. The signal thussupplied to control device 42 is etlcctive to provide a fasteradjustment of pressure in accordance with the magnitude of the signalprovided by sensors 15-13. In this circuit, resistance 67 andcapacitance 63 may be varied as the speed of strip 10 varies to obtain afast response of pressure adjustment for all speeds of the strip. Toeffect this result, I provide means for varying the values of resistance67 and enpacitance 68 with the speed of roll 8 comprising a speedresponsive device 71 which may be, for example, a tachometer and whichis connected to vary the values of circuit elements 67, 63. Suchconnection may be any conventional mechanical or equivalent electricallinkage, such as motor 72, between device 71 and circuits elements 67,68.

While I have shown my arrangements for sensing lateral movement of astrip positioned between each of stands 1, 2, 2, 3, and 3, 4, in manyinstances such an arrangemeat may be needed between only the first pairsof stands or the first two pairs of stands. Also, it may be found thatthe arrangement for stiffening the strip is required only between stands5 and 6. Again, while I have shown the use of pressure sensitiveswitches 53 to disable the control apparatus between the preceding setsof glands, it is obvious that a photoelectric relay or similar devicecould be employed for this purpose.

While in the foregoing particular embodiment of my invention have beenshown, it will, of course, be undc stood that the invention is notlimited to these emb ments since many modifications in the arrangementsand in the instrumentalities employed may be made. It is contemplated bythe appended claims to cover all such modifications which fall withinthe true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. The method of automatically tlrcading a rolling mill in which a stripof material is subjected to pressure at displaced points in its travelthrough the mill con prising:

measuring the curvature of the head end of the by contacting an edge ofthe strip adjacent the end at a pair of predetermined points after headend has passed a pressure point and using such measurement to vary thepressure across the width of the strip at the pressure point to producea horizontal bending of the head end in a direction to guide it towardthe center line of the mill.

2. The method of automatically threading a rolling mill in which a stripof material is subjected to pressure at displaced points in its travelthrough the mill comprising:

measuring the curvature of an edge of the head end of a strip at aplurality of predetermined points after it has passed a pressure point,using such measurement to vary the pressure across the strip as itpasses through the point to produce a horizontal bending of the head endin a direction to guide it to the center line of the mill at the nextpressure point, and after passage of the strip through a subsequentpressure point exerting a vertical force. on the head end to produce acurvature of the strip in a vertical plane to increase the stiffness ofthe strip in its direction of travel. 3. Apparatus for automaticallythreading a rolling mill cf the type in which a strip of material issubjected to pressure at successive points as the material passesthrough the mill comprising:

means for measuring the displacement from a desired position of the edgeof the head end of. a strip of material at a plurality of points afterit has travelled a predetermined distance past a pressure point, and

means responsive to said measuring means for vary the pressure on thematerial at the point to control the horizontal position of the head endof the material.

4. Apparatus for automatically threading a rolling mill of the type inwhich a strip of material is subjected to pressure at successive pointsas it passes through the mill comprising:

means for contacting the edge of the head end of the material at aplurality of spaced points after it has travelled a predetermineddistance past a pressure point to sense the position of the edge at eachof such points relative to the ceutcr line of the mill, and meansresponsive to said edge contacting means for controlling thedistribution of pressure across the width of the material at thepressure point to control the horizontal movement of the head end of thenuterial after it passes the pressure point so that the materialadvances along the center line or" the mill.

5. The apparatus of claim 4 in which the e"" contacting means comprisesa plurality of rollers poo tinned strip head such material and means toproduce a signal varying with horizontal positions of said rollers.

5 6. The method of automatically threading a rolling mill of the type inwhich a ltrip of material is subjected to pressure at displace points inits travel through the mill comprising:

applying a predetermined pressure to such strip as it passes a firstpoint; measuring any horizontal curvature in the strip after its headend has passed the first pressure point;

using such measurement to vary the pressure across the Width of thestrip at the first pressure point to produce horizontal bending of thehead end of the strip in a direction to guide it toward the center lineof the mill, and

reverting to the predetermined pressure at the first point after thestrip enters the next pressure point.

7. The method of automatically threading a rolling mill in v, icll astrip of material is subjected to pressure at dis laced points in itstravel through the mill comprising:

applying a predetermined pressure to the strip at a first point as itpasses through the mill,

measuring any lateral curvature in the head end of the strip after ithas passed such first point,

using such measurement to vary the pressure across the strip at thefirst point to produce a horizontal bending of the strip in a directionto guide it to the center line of the mill,

reverting to the predetermined pressure after the strip enters the nextsuccessive pressure point,

after passage of the strip through a pressure point subsequent to thefirst point exerting a vertical force on the strip to produce acurvature of the strip in a vertical plane to increase the stillness ofthe strip in its direction of travel, and

removing such force after the strip has passed through the nextsucceeding pressure point.

8. Apparatus for automatically threading a rolling mill of the type inwhich a strip of material is subjected to pressure at successive pointsas the material passes through the mill comprising:

means for exerting a predetermined pressure on the strip at a firstpressure point,

means for sensing any lateral curvature of the head end of the stripalter it has travelled a predetermined distance past such first pressurepoint,

cans controlled by said sensing means for varying the pressure acrossthe material at the first pressure point to control the horizontalposition of the material,

additional means for sensing the lateral curvature of the head end ofthe strip alter it has travelled a second predetermined distance pastsaid first pressure point, and

means responsive to said additional means for adjusting said pressurevarying means.

The apparatus of claim 8 including means operaatter the strip has passedthe next pressure point for disabling said pressure varying means andfor returning to the predetermined pressure at said first point.

10. Apparatus for automatically threading a rolling mill of the type inwhich a strip of material is subjected to pressure at successive pointsas the material passes through the mill comprisin screw means at a firstof said points for exerting a predetermined pressure on a strip ofmaterial;

means responsive to the horizontal position of the head end of a stripof material after it passes through the first point for controlling thepressure applied at said point, and

means operative after passage of a strip of material through the neatsucceeding pressure point for dis- 0 tive abling said control means andreturning to said predetermined pressure.

11. The apparatus of claim 10 in which the screw responsive meanscomprises a roll and a pair of screws exerting pressure on the ends ofsaid roll, and said pressure varying means comprises means for operatingsaid screws in opposite directions to effect rapid change in thepressure exerted on the strip.

12. Apparatus for automatically threading a rolling mill of the type inwhich a strip of material is subjected to pressure at successive pointsas the material passes through the mill comprising:

means for exerting a vertical pressure on a strip of material after itshead end passes through a pressure point to produce curvature of thehead end of the strip in a vertical plane, and

means operative after the strip of material passes through the nextsucceeding pressure point for disabling said vertical force exertingmeans.

13. The apparatus of claim 12 in which the vertical force exerting meanscomprises a chute having an open ing curved in a vertical plane at thepoint in which the material leaves the chute.

14. The apparatus of claim 12 in which the vertical force exerting meanscomprises means for simultaneously exerting a vertically downward forceat the center of a strip and vertically upward forces at pointsdisplaced laterally from the center of the strip.

15. In a tandem cold rolling mill the combination comprising:

a plurality of stands each comprising a pair of rolls for exertingpressure on a strip of material;

means positioned along the travel of the strip after its head end passesthrough a first of said stands for sensing the position of an edge ofthe strip; means responsive to said sensing means for controlling thepressure applied at said preceding pressure point;

means operative upon passage of the head end of the strip through thenext succeeding pressure point for disabling said pressure controllingmeans and returning the pressure at said first point to a predeterminedvalue;

means operative after passage of the strip through a subsequent pressurepoint for producing a curvature of the head end of the strip in avertical plane to produce stiifness thereof in the direction of itstravel, and

means operative after passage of the head end of the strip through thenext succeeding pressure point for disabling the stiffness producingmeans.

16. Apparatus for automatically threading a rolling mill of the type inwhich a strip of material is subjected to pressure at successive pointsas the material passes through the mill comprising:

means positioned at a first of said points for exerting a predeterminedpressure on a strip of material;

means responsive to horizontal curvature in the head end of the strip ofmaterial after it passes through the first point for controlling thepressure applied at said point, and

means operative after passage of the head end of the strip of materialthrough the next succeeding pressure point for disabling said controlmeans and returning to said predetermined pressure.

17. Apparatus for automatically threading a rolling mill of the type inwhich a strip of material is subjected to pressure at successive pointsas the material passes through the miil comprising:

means positioned at a first of said points for exerting a predeterminedpressure on a strip of material;

means responsive to horizontal curvature in the head end of the strip ofmaterial after it passes through such first point for varying themagnitude of the pressure applied to said point, and

means responsive to the rate of travel of a strip of material throughthe mill for controlling the rate of varying the pressure at said point.

18. The apparatus of claim 17 in which the said pressure magnitudevarying means includes a time constant circuit and said rate varyingmeans includes means for varying the magnitude of the components in saidtime constant circuit.

References Cited by the Examiner UNITED STATES PATENTS 2,261,972 11/41Matthew 271-74 2,289,410 7/41 Dahlstrom 80--56.2 2,292,535 8/42MacChesney 80-56.2 2,331,246 10/43 Stoltz 80-51 2,552,459 5/51 Rice8035.l 2,909,717 10/59 Hulls et al. 8056.1 2,933,626 4/60 Giboney et al.8056.1

FOREIGN PATENTS 607,961 11/60 Canada.

WILLIAM J. STEPHENSON, Primary Examiner.

LEON PEAR, Exmniner.

1. THE METHOD OF AUTOMATICALLY THREADING A ROLLING MILL IN WHICH A STRIPOF MATERIAL SUBJECTED TO PRESSURE AT DISPLACED POINTS IN ITS TRAVELTHROUGH THE MILL COMPRISING: MEASURING THE CURVATURE OF THE HEAD END OFTHE STRIP BY CONTACTING AN EDGE OF THE STRIP ADAJCENT THE HEAD END OF APAIR OF PREDETERMINED POINTS AFTER SUCH HEAD END HAS PASSED POINT ANDUSING SUCH MEASUREMENT TO VARY THE PRESSURE ACROSS THE WIDTH OF THESTRIP AT THE PRESSURE POINT TO PRODUCE A HORIZONTAL BENDING OF THE HEADEND IN A DIRECTION TO GUIDE IT TOWARD THE CENTER LINE OF THE MILL. 3.APPARATUS FOR AUTOMATICALLY THREADING A ROLLING MILL OF THE TYPE INWHICH A STRIP OF MATERIAL IS SUBJECTED TO PRESSURE AT SUCCESSIVE POINTSAS THE MATERIAL PASSES THROUGH THE MILL COMPRISING: MEANS FOR MEASURINGTHE DISPLACEMENT FROM A DESIRED POSITION OF THE EDGE OF THE HEAD END OFA STRIP OF MATERIAL AT A PLURALITY OF POINTS AFTER IT HAS TRAVELLED APREDETERMINED DISTANCE PAST A PRESSURE POINT, AND MEANS RESPONSIVE TOSAID MEASURING MEANS FOR VARYING THE PRESSURE ON THE MATERIAL AT THEPOINT TO CONTROL THE HORIZONTAL POSITION OF THE HEAD END OF THEMATERIAL.